This invention relates to an improved preventive knee brace. More particularly, this invention relates to an improved single-sided preventive brace for use by athletes to protect the knee joint against damage from lateral impact.
The knee joint is composed of three separate bones and associated ligaments binding them together. At the joint, the lower end of the femur meets the upper end of the tibia. The kneecap, or patella, lies across the front of the joint. On the lateral and medial sides of the adjacent ends of the femur and tibia are a pair of knuckle-shaped protrusions, or condyles. The condyles of the femur rest upon the adjacent condyles of the tibia, which provide a wide base of support for the joint. The condyles also serve as points of attachment for the associated ligaments and muscles which bind the bones together to form the joint.
These bones and ligaments form a complex, hinge-type joint which restricts movement of the lower leg to a single plane. In operation, the joint involves gliding, rolling, and rotational movements which cause it to shift forward during extension of the lower leg and backward during flexion. This shifting results from the interaction of the uneven adjacent condyle surfaces.
Because of its limited planar movement, the knee joint is peculiarly susceptible to damage. Injury to the joint is caused in many cases by sudden movement to the side, such as a quick change of direction in running, or by a lateral blow to the joint. With the foot planted, the tibia is relatively fixed. A sideways blow to the femur may cause it to move laterally relative to the tibia, tearing the associated ligaments and upper leg muscles from the joint. A blow to the tibia when the foot is raised may cause similar damage to the lower leg.
Knee braces fall into two general functional categories, rehabilitative and preventive. Both typically comprise a pair of elongated support bars extending along one or both sides of the leg and hinged at the knee joint.
Rehabilitative braces use the support bars and connecting hinge, often in conjunction with a cast, to relieve stress on a weakened joint. A rehabilitative brace also deliberately limits the normal flexion and extension of the leg and prevents sideways movement of the joint. With the joint's movement limited, the muscles and ligaments can reattach to the bones and heal internal tears. Many rehabilitative braces permit the leg's range of motion to be gradually increased so that the user can strengthen the ligaments and muscles by moving and working them. Rehabilitative braces are usually heavy and cumbersome and restrict mobility. Therefore, they are unsuitable for use by athletes who need maximum freedom of leg motion.
In contrast, preventive knee braces are worn by athletes solely to prevent an injury. They are designed to protect the knee by preventing sideways movement of the femur relative to the tibia without hindering the normal flexion or extension of the leg. This sideways movement can occur either from internal stress on the joint caused by a rapid change in direction during fast movement or from external stress caused by a lateral blow to the knee joint from a block or tackle. Ideally, to provide the necessary protection without interfering with the user's mobility, preventive braces should be strong, laterally rigid, lightweight, and not cumbersome. They should also shield the knee from lateral blows in all positions of leg flexion. Heretofore, preventive braces have not fulfilled all of these objectives.
U.S. Pat. No. 4,337,764 to Lerman discloses the principal drawbacks of a rehabilitative brace. The brace has a pair of bars extending along one side of the leg and pivotally connected outside the knee joint at a plate assembly defining a polycentric clevis joint. The bars are embedded in a plaster cast to rigidify the bars and provide support at the knee joint for limited movement of the leg while in the cast. The adjacent ends of the bars meeting at the joint have intermeshing teeth to force both bars to pivot interdependently, allowing the user to use the muscles of his upper leg, for example, to extend or flex the lower leg or vice versa. Adjustable stops on the plate assembly further limit the maximum angular movement of the leg in flexion or extension. Such limitations on joint motion may aid in healing torn ligaments but render the brace unacceptable for active wear. The interdependent and limited movement of the bars in conjunction with the heavy, cumbersome plaster casts would obviously and severely inhibit mobility.
Other rehabilitative braces suffer from similar limitations on mobility. U.S. Pat. No. 4,372,298 to Lerman discloses a cumbersome, double-sided brace with U-shaped upper and lower yoke-like support members fitting around the back of the leg. Upper and lower bars interconnecting the support members at opposite sides of the leg pivot interdependently at a pair of polycentric clevis joints within massive knee plate assemblies to limit free movement of the knee joint. Flexion of the leg in particular is curtailed by the close fitting and firmly attached support members. U.S. Pat. No. 4,361,142 to Lewis et al. and Canadian Patent No. 1,011,204 to Patel also feature supportive but cumbersome, motion-inhibiting double-sided bracing similar to that of the brace of Lerman --298, and have many of the same limitations. U.S. Pat. No. 4,340,041 to Frank discloses a knee splint with long, thin upper and lower leg bars embedded in plaster casts and joined to each other at a single-pivoting joint connection. The connection is adjustably set to hold the leg member at a selected angle to promote proper healing of the knee joint. However, the set splint prevents any flexion of the leg.
Several of the rehabilitative braces, such as those of Patel and Lerman '298, are also suggested for use as preventive braces. Their double-sided bracing and laterally rigid clevis joints provide limited protection against sideways joint displacement from a severe lateral blow to the knee, but their massive structure and necessarily heavy weight limit free movement of the leg and would induce fatigue. Moreover, their complexity makes them difficult to mount properly to the leg.
Braces designed solely for prevention of athletic injury, on the other hand, typically have single-sided bracing to reduce bulk and weight, and to permit greater freedom of leg movement. The single-sided bracing extends along one side of the leg to prevent sideways movement of the joint caused by sudden changes in running direction. For example, U.S. Pat. No. 4,249,524 to Anderson discloses a single-sided preventive brace having a long and narrow support bar positioned alongside the knee joint. Short, padded plates extending along the upper and lower leg are pivoted at lap joints to each end of the bar. The support bar provides a double-hinged connection between the upper and lower leg which tends to keep them laterally aligned. However, the Anderson brace does not adequately shield the knee joint from a lateral blow in all leg positions. When the leg is flexed, the narrow bar bridges the upper and lower leg behind the knee, exposing it to lateral impact. Moreover, its lap joints provide a poor shield even when the bar covers the knee joint because they are inherently weak, introducing undesirable lateral flexibility to the brace which can result in the transfer of force from a severe lateral blow through the bar directly to the knee.
U.S. Pat. No. 3,528,412 to McDavid discloses another single-sided preventive brace. Its long, thin upper and lower leg members are pivotally interconnected at a single lap joint in the general area of the knee. Its single pivot cannot accurately mimic the complex motion of the knee, thereby leaving the knee unprotected and thus vulnerable to lateral impacts when the leg is flexed. Because of its laterally weak lap joint and thin leg members, the McDavid brace is quite flexible laterally and therefore does not protect the knee from the force of severe lateral blows even when its joint coincides with the knee joint.
A further drawback of existing preventive knee braces is that they are difficult to repair and must usually be returned to the manufacturer for this purpose. This is not only time-consuming but also requires each user to keep a spare one of these custom-fitted braces on hand, effectively doubling their cost.
Accordingly, a need remains for a one-sided preventive knee brace that is lightweight, strong and laterally rigid, and yet effectively shields the knee joint throughout its full range of motion without hindering normal leg movement. There is also a need for such a brace that is quickly and easily repairable by the user or his athletic staff. These are the primary objectives of the present invention.